<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
    <style>
        .bar {
            width: 200px;
            height: 30px;
            border: 1px solid #c23903;
            /* 圆角边框 */
            border-radius: 15px;
            margin:100px auto;
            /* 溢出隐藏 */
            overflow: hidden;
        }

        .bar_in {
            /* 儿子的宽度，可以设置百分百，百分百相对于父亲的宽度 */
            width: 70%;
            height: 30px;
            line-height: 30px;
            text-align: center;
            background-color: red;

        }
    </style>
</head>

<body>
    <div class="bar">
        <div class="bar_in">正在加载中</div>
    </div>
</body>

</html>